At the end, they found an actual treasure chest filled with Harry Potter sticker sheets ... See, the real prize was that I taught them a new spell...Bubbleardium Leviosa You can create a clue ...

It's a well-known fact among longtime fans of the Harry Potter series that the most dangerous spells of the Wizarding World are the Unforgivables — Avada Kedavra, Crucio, and Imperio.